The Bosch and the Chiaphua are both excellent for driving. The versatility and relative ease of use of the Bosch drill motors for drive applications is unparalleled, and many teams use them for that very reason. They are a safe choice, and a strong choice as well. As Paul Copioli pointed out, we have found the CIMs to be very good in both directions and they are fine even after long use. They are actually usually colder on the exterior after a match than anthing else we've used in recent memory, including the drills and Fisher-Prices. For Fisher-Prices and drills (which clearly aren't meant to be used nonstop and stalling for two minutes), I highly recommend some kind of compressed air cooling spray to use between matches.
Many older teams with the means to build a gearbox do so in order to get CIMs and Bosch drills running together (i.e. four-motor drive). That way they can run at relatively high speeds while maintaining the power they need in order to hold their own. Or even have a transmission in addition to the four motors. Some teams (including 217 in 2002 and 188 for the past two years) mate three motors per gearbox for a whole lot of power. Or at least power drain; by the latter third of a match, these robots tend to be out of juice. Last year we built a simple gearbox that mated the Bosch drills, CIMs, and Fisher-Price motors so that we could run at high speeds and still outpush the vast majority of our opponents. We did have some trouble with our battery voltage dropping low enough to cut out our controller in two matches (one of which being the finals in the Canadian Regional
), but those were very extreme circumstances.
While we have used Fisher-Price motors in our drivetrain before, we don't use them by themselves. Depending on the configuration of a robot, in some cases they won't be able to even turn it, and then you'll get the distinctive toasty Fisher smoke and smell.